Crack Identification in Gear Tooth Root Using Adaptive Analysis

2007 ◽  
Vol 348-349 ◽  
pp. 697-700
Author(s):  
Ales Belsak ◽  
Jože Flašker
Keyword(s):  
Fatigue Crack ◽  
Signal Analysis ◽  
Gear Tooth ◽  
Crack Identification ◽  
Test Plant ◽  
Tooth Root ◽  
Dynamic Parameters ◽  
Unit Operation ◽  
Tooth Stiffness ◽  
Non Stationary Signal

Problems concerning gear unit operation can result from various typical damages and faults. A crack in the tooth root, which often leads to failure in gear unit operation, is the most undesirable damage caused to gear units. This article deals with fault analyses of gear units with real damages. A laboratory test plant has been prepared; it has been possible to identify certain damages by monitoring vibrations. In concern to a fatigue crack in the tooth root significant changes in tooth stiffness are more expressed. When other faults are present, however, other dynamic parameters prevail. Signal analysis has been performed also in concern to a non-stationary signal, using the adaptive transformation for signal analysis.

Vibration Analysis of Gears with Fatigue Crack in Tooth Root

2006 ◽  
Vol 324-325 ◽  
pp. 835-838
Author(s):  
Aleš Belšak ◽  
Jože Flašker
Keyword(s):  
Fatigue Crack ◽  
Laboratory Test ◽  
Signal Analysis ◽  
Vibration Analysis ◽  
Operating Conditions ◽  
Test Plant ◽  
Tooth Root ◽  
Unit Operation ◽  
Time Frequency ◽  
Non Stationary Signal

A crack in the tooth root, which often leads to failure in gear unit operation, is the most undesirable damage caused to gear units. This article deals with fault analyses of gear units with real damages. Numerical simulations of real operating conditions have been used in relation to the formation of those damages. A laboratory test plant has been used and a possible damage can be identified by monitoring vibrations. The influences of defects of a single-stage gear unit upon the vibrations they produce are presented. Signal analysis has been performed also in concern to a non-stationary signal, using the Time Frequency Analysis tools. Typical spectrograms, which are the result of reactions to damages, are a very reliable indication of the presence of damages.

Investigating Vibration Sources of Faulty Gear Units

2008 ◽  
Vol 385-387 ◽  
pp. 601-604
Author(s):  
Ales Belsak ◽  
Joze Flasker
Keyword(s):  
Signal Analysis ◽  
Analysis Tool ◽  
Tooth Root ◽  
Dynamic Parameters ◽  
Unit Operation ◽  
Time Frequency ◽  
Tooth Stiffness ◽  
Non Stationary Signal ◽  
High Degree ◽  
Very High

A crack in the tooth root is the least desirable damage of gear units, which often leads to failure of gear unit operation. A possible damage can be identified by monitoring vibrations. The influences that a crack in the tooth root of a single-stage gear unit has upon vibrations are dealt with. Changes in tooth stiffness are much more expressed in relation to a fatigue crack in the tooth root, whereas in relation to other faults, changes of other dynamic parameters are more expressed. Signal analysis has been performed in relation to a non-stationary signal, by means of the Time Frequency Analysis tool, such as Wavelets. Typical scalogram patterns resulting from reactions to faults or damages indicate the presence of faults or damages with a very high degree of reliability.

Investigating Faulty Gear-Unit Vibration

2010 ◽  
Vol 452-453 ◽  
pp. 429-432
Author(s):  
Aleš Belšak ◽  
Jože Flašker
Keyword(s):  
Fatigue Crack ◽  
Wavelet Function ◽  
Operating Conditions ◽  
Tooth Root ◽  
Dynamic Parameters ◽  
Unit Operation ◽  
Dynamic Reaction ◽  
Time Frequency ◽  
Tooth Stiffness ◽  
Non Stationary Signal

A crack in the tooth root is probably the least desirable problem in gear unit operation; it often leads to failure. Signals produced by a gear with a crack in the tooth root, produced through real operating conditions, and signals caused by a faultless gear are used for the analysis. By monitoring vibrations it is possible to detect the presence of a crack. A fatigue crack in the tooth root brings about significant changes in tooth stiffness. Other faults are usually linked with modifications of other dynamic parameters. Time Frequency Analysis tools, e.g. Wavelets Analyses, are used to analyse a non-stationary signal. The wavelet transform is chosen for the analysis. The wavelet function similar to the dynamic reaction of the crack in the tooth root is selected. By means of the methods and the analysis presented in this paper, the reliability of determining modifications in signal vibrations is improved.

Gear Tooth Root Fatigue Assessments by Estimating the Real Stress Cycle

2007 ◽  
Author(s):  
Damir T. Jelaska ◽  
Srdjan Podrug
Keyword(s):  
Fatigue Crack ◽  
Numerical Models ◽  
Gear Tooth ◽  
Moving Load ◽  
Force Model ◽  
Tooth Root ◽  
Stress Cycle ◽  
Linear Elastic ◽  
Moving Force ◽  
Elastic Fracture

A several kinds of numerical models, including moving force model, for determination the service life of gears in regard to bending fatigue in a gear tooth root, is presented. Finite element method and linear elastic fracture mechanics theories are then used for the further simulation of the fatigue crack growth under a moving load. Moving load produces a non-proportional load history in a gear’s tooth root. The corresponding stress cycle is obtained which enables more precise computing. An approach that accounts for fatigue crack closure effects is developed to propagate crack under non-proportional load. The computational results are compared with other researchers’ numerical results and with service lives of real gears. The fatigue lives and crack paths determined in this paper exhibits a substantial agreement with experimental results and significant improvement compared with the existing numerical models.

Numerical Modelling of the Crack Propagation Path at Gear Tooth Root

2003 ◽  
Author(s):  
Damir T. Jelaska ◽  
Srecko Glodez ◽  
Srdjan Podrug
Keyword(s):  
Fatigue Crack ◽  
Service Life ◽  
Crack Propagation ◽  
Experimental Testing ◽  
Gear Tooth ◽  
Fatigue Crack Initiation ◽  
Propagation Path ◽  
Tooth Root ◽  
Stress Cycles

A numerical model for determination of service life of gears in regard to bending fatigue in a gear tooth root is presented. The Coffin-Manson relationship is used to determine the number of stress cycles Ni required for the fatigue crack initiation, where it is assumed that the initial crack is located at the point of the largest stresses in a gear tooth root. The simply Paris equation is then used for the further simulation of the fatigue crack growth, where required material parameters have been determined previously by the appropriate test specimens. The functional relationship between the stress intensity factor and crack length K = f(a), which is needed for determination of the required number of loading cycles Np for a crack propagation from the initial to the critical length, is obtained numerically. The total number of stress cycles N for the final failure to occur is then a sum N = Ni + Np. Although some influences were not taken into account in the computational simulations, the presented model seems to be very suitable for determination of service life of gears because numerical procedures used here are much faster and cheaper if compared with the experimental testing.

Comparison of Numerical Models for Gear Tooth Root Fatigue Assessments

2005 ◽  
Author(s):  
Damir T. Jelaska ◽  
Srdjan Podrug ◽  
Srecko Glodez
Keyword(s):  
Fatigue Crack ◽  
Service Life ◽  
Numerical Models ◽  
Experimental Testing ◽  
Gear Tooth ◽  
Moving Load ◽  
Fatigue Crack Initiation ◽  
Homogeneous Material ◽  
Force Model ◽  
Tooth Root

A several kinds of numerical models, including moving force model, for determination the service life of gears in regard to bending fatigue in a gear tooth root, is presented. The critical plane damage model, Socie and Bannantine [1], 1988, has been used to determine the number of stress cycles required for the fatigue crack initiation. This method determines also the initiated crack direction, what is good base for a further analyses of the crack propagation and the assessment of the total fatigue life. Finite element method and linear elastic fracture mechanics theories are then used for the further simulation of the fatigue crack growth under a moving load. Moving load produces a non-proportional load history in a gear’s tooth root. An approach that accounts for fatigue crack closure effects is developed to propagate crack under non-proportional load. Although some influences (non-homogeneous material, traveling of dislocations, etc.) were not taken into account in the computational simulations, the presented model seems to be very suitable for determination of service life of gears because numerical procedures used here are much faster and cheaper if compared with the experimental testing. The computational results are compared with other researchers’ numerical results and with service lives of real gears. The fatigue lives and crack paths determined in this paper exhibits a substantial agreement with experimental results and significant improvement compared with the existing numerical models.

Delay-Bond Graph Models for Geared Torsional Systems

1974 ◽  
Vol 41 (2) ◽  
pp. 366-370 ◽  
Author(s):  
N. T. Tsai ◽  
S. M. Wang
Keyword(s):  
Transmission Line ◽  
Gear Tooth ◽  
Nonlinear Damping ◽  
Bond Graph ◽  
Dynamic Responses ◽  
State Variables ◽  
Graph Models ◽  
Wave Variables ◽  
Tooth Stiffness ◽  
Line Elements

The dynamic responses of geared torsional systems are analyzed with the delay-bond graph technique. By transforming the power variables into torsional wave variables, the torsional elements are modeled as transmission line elements. The nonlinear elements, e.g., varying tooth stiffness, gear-tooth backlash, and nonlinear damping, are incorporated into the ideal transmission line element. A computational algorithm is established where the state variables of the system are expressed in terms of wave scattering variables and the dynamic responses are then obtained in both time and space domains. The simulation results of several simple examples of linear and nonlinear geared torsional systems are presented to demonstrate the feasibility of this algorithm.

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